Approximately 10% of students have singing difficulties appearing as poor pitch singing. During the period 2012 to 2014, I assessed 2390 recordings from 239 students. 25 students were graded below C, and thus were defined as poor pitch singers (PPS). However, these students showed varying patterns of mastery within their own portfolios of recordings. This raised the initial research question: Are there features within the musical material itself that can explain the varying degrees of mastery? The best and the weakest performances of the PPS were analyzed in terms of musical structures and lyrics. Features of the singing repertoire, self-concept and practice appear to influence singing development with PPS.